Here is a quick question for you. If you could legally save $50 million in tax, would you do it?

The late Kerry Packer certainly would.

A quarter of a century ago he famously stared down politicians who were questioning him about the tax practices of Australian Consolidated Press.

"Of course I'm minimising my tax," Packer bellowed.

"If anybody in this country doesn't minimise their tax they want their head read. As a government I can tell you you're not spending it that well that we should be paying extra."

It is an exchange that made front page news at the time and has become part of Australian political folklore.

Mr Packer was on the front foot defending his business methods and he wasn't going to allow the nation's leaders to get in his way.

Now tax avoidance by big companies is back in the spotlight with a Senate inquiry hearing how billions of dollars in revenue earned in Australia is funnelled overseas to lower-taxing jurisdictions.

Mr Packer would be pleased to know that Australian companies are just as good at tax avoidance as big multinationals, with companies like BHP Billiton, Rio Tinto and News Corporation leading the way (whether those companies really are still Australian though is another story).

Fortunately for today's politicians, today's business leaders are not as ferocious as Kerry Packer, so the members of the Senate inquiry into tax avoidance were able to give as good as they got.

In fact, all the businesses leaders who appeared before their inquiry were unfailingly polite.

What we learned is that among other things, US hi-tech giants Apple, Google and Microsoft shift nearly all the money they generate in Australia to places like Singapore, Bermuda and Ireland.

And we are talking many billions of dollars.

Which brings me back to my initial question.

Microsoft's global head of tax, Bill Sample, told the Senate inquiry that in 2014 his company billed all its Australian software sales through Singapore - $2 billion worth in fact.

For argument's sake, let's assume 20 per cent, or $400 million, of that money was profit.

You have no doubt been hearing a lot about the Paris Agreement and know that it pertains to climate change, but are too embarrassed at this stage to ask for an overall explanation of what it's all about.